Are You Grounded?

In this post we are going to discuss the importance of grounding and lightning arrestors on your solar system. Did you know that at any time there are over 2,000 thunderstorms going on around the world? These storms produce about 100 lightning strikes per second. And based on NASA’s findings, over 90% of lightning strikes happen over land. Fun fact: the longest recorded lightning strike was 121 miles long.

Solar systems can be severely damaged or destroyed by lightning even if they do not take a direct hit. A direct hit is actually very uncommon, but damage happens often. The damage comes from the electron charge in the air or ground that travels to the system. If you don’t give it any place to go, it can wreak havoc on your equipment.

The first and most important way to save your equipment is through proper grounding. This means the entire system – from the panel array, to the charge controller and inverter, and yes, even the batteries. Even though batteries can absorb some energy, they cannot handle it all. And if they are not grounded, that back feed can take out the charge controller and/or the inverter and even permanently damage the batteries. The best way to ground your existing system is to install at least (1) 8’ long copper rod into wet soil (buried vertically with only enough above ground to connect to your grounding wire). This gives the electrons a great path to dissipate back into the ground. Yes, I know this is Arizona in the high desert; wet ground is not that easy to find. The best alternative option in our area is solid ground such as clay or solid soil. If this is not possible, you have two other options. One is install multiple rods staggered in different areas and tied together with bare #6 copper grounding wire. And the second option is to install 100’ of bare #6 copper ground wire in a trench leading away from the house. If you are building a new house and pouring a concrete footer, ground to the rebar inside this footer. This creates the best ground for the system.

This direct path to ground will significantly improve the chances of your system surviving a thunderstorm. However, even with a grounding rod you can still get enough stray voltage to damage sensitive electronics in your charge controller and/or inverter. For this reason, we also recommend installing in-line surge arrestors on your system. These lightning (surge) arrestors are designed to absorb the stray power so it can pass through the system without destroying your equipment. They are a lot like the surge protector into which you plug your TV to protect it. Some surge arrestors such as the Midnite Solar have two blue LED lights on them to signify that they are working properly and protecting your equipment. These are the type we recommend so you can see they are doing their job. Some other brands may be slightly cheaper but do not give you this valuable visual indicator.

For more information on this subject, you can contact us here at AZ Off-Grid Living or look up The National Electrical Code (NEC), Article 250 and Article 690.41 through 690.47. Be sure to specify code-compliant wire sizes, materials, and techniques.